The Justice Department (DOJ) announced Friday that Sessions called for the former attorneys to resign. Of the 93 U.S. attorneys, 46 remain from the past administration, according to the DOJ.

The call for resignations applies to all Senate-confirmed U.S. Attorneys, including Bharara.

It came as a surprise, as Bharara reportedly met with Trump after the election and agreed to remain in his position during the Trump administration. Sessions also asked him to stay, the prosecutor told The New York Times.

According to an exclusive report by The Daily Beast late Friday, Bharara told his section chiefs that he’d yet to submit the requested letter and may instead challenge Sessions to fire him.

Bharara's office is working through an investigation of New York City Mayor Bill de Blasio and about to start the trials of two close allies to New York Gov. Andrew Cuomo.

Bharara built a reputation in New York by going after big banks and Wall Street.

He's prosecuted nearly 100 Wall Street executives and brought legal challenge to the four largest banks in the U.S. He also closed a multi-billion dollar hedge fund as part of an insider trading settlement.